Device for uniting tubular articles with sealing elements in a gastight manner

ABSTRACT

An oven device suitable for uniting in a gastight manner a plurality of tubular envelopes of densely sintered material having sealing members at both ends. The oven device can be made to cooperate with a vacuum system and a gas supply and comprises a U-shaped heating member of graphite where the envelopes, situated in a row between the limbs of the heating member are locally heated.

[ 1 Feb. 29, 1972 United States Patent Van Bragt Dadson..... 5/1962Allen, Jr... 3,192,006 6/1965 Algatt et al 3,403,212 9/1968Sato.......... 3,404,874 10/1968 Wynne......

3,546,348 12/1970 De Corso..

[22] Filed: Feb. 17, 1970 Primary Examiner-John F. Campbell AssistantExaminerRichard Bernard Lazarus Att0rney-Frank R. Trifari [21] Appl. No;

[30] Foreign Application Priority Data ABSTRACT An oven device suitablefor uniting in a gastight manner a plurality 'of tubular envelopes ofdensely sintered material having sealing members at both ends. The ovendevice can be made to cooperate with a vacuum system and a gas supplyand comprises a U-shaped heating member of graphite where the envelopes,situated in a row between the limbs of the heating 5 0083 w wnw 2 09.l.8,1 9 l1 6 20% H/ H 3 9 0 /01.. m 3R2 m 2 0 42 30 O m H3 1 w m 3 m1& mu d um e u m m u e n N um In 9 0 m q m d w M F UmF 1]] 218 555 [[i.

member are locally heated.

References Cited UNITED STATES PATENTS 6 Claims, 6 Drawing FiguresPatented Fel a. 29, 1972 4 Sheets-Sheet 1 IN VENTOR.

B JOHANNES M. VAN BRAGT -i f.

AGENT 4 Sheets-Sheet 2 lu lllll'll'lll fig.2

INVENTOR.

BYJOHANNES M. VAN BRAGT AGENT Patented Feb. 29, 1972 4 Sheets-Sheet 3livvENToR.

BYJOHANNES M. VAN BRAGT AGENT Patentd I Feb. 29,

4 Sheets-Sheet 4 IN VENTOR.

BYJOHANNES u. was BRAGT AGENT DEVICE FOR UNITING TUBULAR ARTICLES WITH'SEALING ELEMENTS IN A GASTIGI-IT MANNER in which the envelope of thedischarge space consists of transparent densely-sintered aluminum oxideand comprises at least one current supply member which is secured in theenvelope in a gastight manner. The product described in said patent ap-..plication comprises a tubular body which at one end comprises acylindrical'portion in which a sealing element consisting ofatransparent densely sintered aluminum oxide is situmember is-secured ina gastight manner by means of a solder glass having a melting pointhigher than 800 C. and lower than the melting point of the transparentdensely sintered aluminum oxide and that of the metal of the currentsupply member. This lamp is'furthermore provided with a cover consistingof transparent densely sintered aluminum oxide and bearing against theend of the cylindrical portion of the envelopeand against the sealingelement situated therein, said cover comprising an aperture for thecurrent supply member and beingsecured in a gastight manner to theenvelope, the sealing element, and the current supply member by means ofa solder glass having a melting point higher than 800 C. and lower thanthe melting point of the transparent densely sintered aluminum oxide andthat of the metal of the current supply member.

The said published Dutch patent application also describes how such aproduct can in principle be manufactured. The

method used in said patent application is a chamber process in which thechamber is formed by a glass bell placed in the holder and evacuated orfilled with an inert gasand in which adhesive. In said glass bell isfurthermore arranged an annular member of graphite around the parts ofthe tubular article to be heated, said member being heated by means of ahighfrequency field applied outside the glass bell in such manner thatthe radiant heat necessary for uniting the tube and the "sealing memberis produced in the graphite ring. So the article is only heated at itsend, so locally.

Thedevice described in the above-mentioned patent application is inprinciple suitable only to provide one article with a sealing member andhence less suitable for use in the manufacture of large series of saidlamps.

Starting from the mounting principle described in the above-mentionedpatent application, the object of the present invention is to provide adevice with which a number of tubular articles can be simultaneouslyprovided with a sealing member supporting an electrode.

The deice according to the invention is characterized in that itcomprises an oven which can be made to communicate with a vacuum systemand, if desirable, with a gas dosing system in which at least twoparallel arranged striplike heating members are'rigidly secured and areconnected to a voltage source the device furthermore comprising at leastone holder in which the tubular articles which are each provided with asealing member can be arranged in a row, if desirable with theinterposition of an adhesive, said holder being arranged in the oven insuch a manner that the articles are situated with their ends between thetwo strip-shaped current conveying heating members. So the oven meanthere is a chamber oven. By introducing the strip-shaped heating elementswhich convey current by the direct connection to a voltage source andoperate as heat radiators, it has surprisingly been found possible toheat the articles which are arranged in one or more rows simultaneouslyat their ends in a satisfactory manner. So the conventionalhigh-frequency heating via a graphite ring around each of the articlesmay be omitted. This presents the possibility of using very compactapparatus; a bulky high-frequency apparatus is superfluous. Since no useis made of graphite rings which arearranged around the articles, it isalso possible to arrange said articles are short distance from eachother in which it has appeared that even good results are obtained whenthe walls of the strip-shaped heating members facing each other arearranged in plane parallel.

By manufacturing said strip-shaped heating elements-from graphite andcausing them to extend as the limbs of U-shaped profile, the additionaladvantage is obtained that it is sufficient for said U-shaped element tobe secured only at its free ends; the rigidity of such a U-shapedelement has been found to be large enough, while in addition thermalstresses in said element are avoided substantially entirely when it issecured in this manner; actually it can expand freely in thelongitudinal direction of the strip-shaped limbs.

According to a practical embodiment the oven comprises at least onesealing ring, in which the heating members are secured in one part andthe holder can be placed on or is formed by the other part.

In order that the invention may be readily carried into effect, oneembodiment thereof will now be described in greater detail, by wayofexample, with reference to the accompanying drawings, in which:

FIG. 1 shows a lamp to be composed which contains an envelope ofsintered material;

FIG. 2 is a diagrammatic side elevation of an oven used in composingsaid lamp;

FIG. 3 is a cross-sectional view taken on the line III-III of FIG. 2;

FIG. 4 is a cross-sectional view taken on the lines IV-IV of FIG. 3 ofthe holder to used with the oven shown in FIGS. 2

and 3;

FIGS. 5 and 6 are a plan view and a side elevation, respectively, of theheater device used in the oven.

FIG. 1 shows a part of a discharge lamp as is described in the publishedDutch Pat. application No. 6,704,681. This lamp comprises a tubularenvelope of transparent densely sintered aluminum oxide. Current supplymembers 3 and 5 of niobium are situated at either end of the envelope 1.Two sealing elements which likewise consist of transparent denselysintered aluminum oxide are denoted by 7 and 9 and are secured hi theenvelope 1 by sintering. Also, 11 and 13 denote two covers which alsoconsist of densely sintered aluminum oxide. Also, 15 denotes a solderglass with which the current supply member 3 is secured both to thecover 11 and to the sealing element 7. This solder glass is also presentbetween the cover 1 l and the-sealing element. The electrode of the lampconsists of a tungsten rod 17 secured in the current supply member 3 bymeans of a titanium solder 19. This rod comprises a tungsten coil 21;the coil may be covered with a material which readily emits electrons.

In manufacturing said lamp, the envelope 1 is first provided with thetwo sealing elements 7 and 9 which comprise each a central aperture inaccordance with the abovementioned Dutch patent application. In one endof the envelope 1 the current supply member 3 comprising the parts 17,19, 21 is held and the cover 11 is placed on the sealing element 7 withthe interposition of a ring of glass or a melting ceramic material whichclosely surrounds the member 3. An analogous ring of glass is thenplaced on the cover. A glass material may be used such as the materialdescribed in British Pat. specification No. 1,019,821. The assembly isplaced in a glass bell in which an argon atmosphere is maintained andthe envelope is surrounded at its one end by a ring of graphite which isheated by means of a high-frequency coil arranged outside the glass belland which causes the solder glass to melt. Upon cooling a gastight sealis obtained. The glass bell is then removed. The other end of theenvelope is then provided in an analogous manner with the cover and acurrent supply member 5, again with the interposition of the requiredglass rings. The assembly is then again exposed in the glass bell to athermal treatment of the high-frequency heated ring of graphite.Previously, however, a quantity of mercury and alkali metal is providedin the tubular envelope in which, during the addition of this metal, anargon atmosphere must be maintained in the envelope. Be-

fore heating the tubular envelope in the glass bell, the latter isevacuated for degassing the various components and is then filled withxenon. As aresult of this the interior of the envelope 1 is alsoprovided with said xenon gas. Only then does heating-take place. In thismethod only one glass bell per seal is used. i

In the device according to the invention the same method is used inprinciple. This device comprises a chamber oven which is constructed forsubjecting a large number of tubular envelopes l, for example, 20,simultaneously to the thermal treatment.

The oven used in this device is shown in FIGS. 2 and 3. In theseFigures, 23 denotes a cylindrical portion and 25 an angular portion,between which portions a sealing ring 27 is present. The angular portion25 comprises ducts 26, 28, 30, 32 for water-cooling. This portioncomprises a chamber 31 which can be made to communicate with the vacuumsystem (connection 35) by means of the duct 33. Via this chamber 31 avacuum can extend up to in the cylindrical chamber 37 of the portion 23.This portion 23 comprises a block 39 in which chambers 41,. 43, 45, '47,49 and 51 are recessed which, together with the surrounding jacket 53,constitute a number of chambers which can also be made to communicatewith a water-cooling system. A U-shaped heating member of graphite whichis shown in broken lines in FIG. 2 and is denoted by 55 is arranged insaid portion; in FIG. 3 the limbs of the U are denoted by 57 and 59.This member (see also FIGS. and 6) is secured with its widened poles 61and 63 to two watercooled high-vacuum-tight current lead-in memberswhich are insulated relative to each other and to the oven wall andwhich are coupled to the connection terminals of a voltage source.

This heating member is surrounded by a heat-reflecting screen 65 ofmolybdenum which is supported by the cylindrical chamber 67 in theportion 23 at only a few points of its circumference. A molybdenum plate69 is secured to said screen 65. The two ends of the cylindrical portion23 are closed by covers 71 and 73, the heating member 55 being securedto the cover 71 only via the widened poles 61 and 63. The inner side ofthe cover 73 is provided with a few layers of a heat-reflectingmaterial.

The portions 23 and 25 belong to the stationary part of the oven. Theyfurthermore comprise ducts which open into the chamber 31 and can bemade to communicate with a gas supply device. The ducts 75 and 76communicate with inlets of argon of different pressures, while the ducts77 and 78 can be made to communicate with an inlet and outlet,respectively, for xenon.

The oven furthermore comprises a movable bottom 79 which can close thechamber 31 via sealing ring 80. This bottom 79 comprises a fittingsurface 81 on the upper side of which 20 holders 83 are secured. Theseholders are situated at equal distances from each other. Members 85 areforced upwards in said holders by compression springs 87. Said holdersare constructed for containing the envelopes 1 which at their one endhave to be united with sealing members in a gastight manner.

The bottom 79 bears on the platform 89 which is secured to a verticallymovable rod 91. In a downward position, the bottom 79 can be removedfrom the platform and the holders 83 be provided with tubularenvelopes 1. All this is arranged so that when the bottom part 79 ismoved to its uppermost position, the tubular envelopes in the holdersare just situated with their free ends between the limbs 58 and S9 ofthe U-shaped heating member 55.

The operation with this device is as follows. First the bottom 79 whichis removed from its platform 89 is provided with a numberof tubularenvelopes 1 which are provided at both ends with sealing members 7 and 9secured therein. Analogous to the known method, the free ends thereofare provided with a current supply member 3 and a cover 11 with theinterposition of the glass sealing rings. The assembly is then placed onthe platform in a prescribed position. The bottom is then moved againstthe oven portion, the oven is evacuated andthe oven space is then filledwith argon as a protective gas (l2 cm. of Hg absolute). In thisatmosphere the U- shaped element is heated electrically by the directpassage of current ofapproximately 300 a. at 20 v. When the glass ringsmelt, the pressure by the springs 87 is transferred to the pins 93 whichare temporarily inserted in the current supply members and bear on thewall 69. In this manner the member 3, which has a wire 94 securedthereto and serving as an abutment, is oriented in the envelope 1 in anaccurately prescribed manner. The assembly is cooled while maintainingan argon atmosphere in the oven. The bottom 79 is then removed. Thecycle period for this first sealing in so far as it takes place in theoven is approximately 20 minutes.

The pins 93 are then removed and the envelopes 1 are placed in theholders 83 with their sealed ends. The tubular envelopes l are thenfilled with argon in a vertical position by means of a pipe connected toa supply of argon. While maintaining the flow of argon a pill of sodiumamalgam is dosed in the envelope by means of a dosing device as isdescribed in Dutch Pat. application No. 6,803,906. The cover 13, thecurrent supply member 5 and a set of rings of glass or a melting ceramicare then rapidly placed on the envelope 1. After the 20 holders allcomprise a thus prepared tubular envelope, the bottom 79 is againcoupled to the oven portion 25. Then the oven is evacuated again. Thetime expiring between the dosing of the first pill and the beginning ofevacuation is approximately 4 minutes. Such a small quantity of ambientair is found to diffuse in the envelopes within these 4 minutes that theamalgam pills are not noticeably attacked. When the pressure in the ovenspace is sufficiently low, the heating member is heated at approximately1 ,000 C.

In this position the evacuation is continued for another approximately 3minutes. The communication with the vacuum system is then closed andxenon gas is supplied at a filling pressure of 4 cm. of Hg absolute.Heating is continued until the heating member is heated to l,500 C. Theenvelopes l are thus sealed at their other ends. The xenon gas presentin the oven space outside the envelopes 1 is then recovered via arefreezing process for which purpose reference is made to theabove-mentioned Dutch published Pat. application No. 6,704,681. Coolingin an argon atmosphere takes then place after which the bottom 79 can beremoved again. It takes approximately 20 minutes to provide this secondsealing in so far as the process occurs in the oven.

Although in principle it is possible to operate with one and the sameoven both for the first and the second sealing, it is recommendable touse two ovens of substantially identical shape. One oven then serves forthe first sealing and is constructed for that purpose, while the otheroven serves for the second sealing and is constructed for that secondpurpose. Of course it is alternatively possible to use several pairs ofovens, for example, four ovens, which are operated so that totally onlyone energy source, one vacuum plant, one gas dosing device, one devicefor refreezing xenon are required. The whole assembly of ovens can beoperated by one person.

Although only one row of envelopes can be treated with the deviceaccording to the invention as described, it is of course alternativelypossible to arrange several rows of envelopes parallel to each other inthe same oven space. In that case a few U-shaped heating membersarranged parallel to each other may be used.

What is claimed is:

1. A device for uniting in a gastight manner a number of tubulararticles with sealing elements provided with electrodes at their oneends, characterized in that it comprises an oven which is adapted tocommunicate with a vacuum system and, in which at least two parallelarranged strip-shaped heating members are rigidly arranged and areconnected to a voltage source, the device furthermore comprising atleast one holder in which one end of the tubular articles which are eachprovided with a sealing member can be arranged in a row, said holderbeing arranged in the oven in such manner that each of the articles aresituated with their other end between the two strip-shaped currentconveying heating members wherein the oven comprises at least twoportions which can be separated from each other and between which asealing ring is arranged in which the heating members are secured in oneportion and the holder can be placed on or be formed by the otherportion.

2. A device as claimed in claim 1, characterized in that the two heatingmembers are manufactured from graphite.

3. A device as claimed in claim 2, characterized in that the twostrip-shaped members constitute the limbs of a U-shaped heating'member,which limbs are coupled at their free ends directly to a voltage source.

4. A device as claimed in claim 1, characterized in that one portion isstationary and the other portion is vertically movable.

5. A device as claimed in claim 1, characterized in that the ovencomprises an internal abutment for the ends of the articles to be heatedwhich are arranged so as to be resilient in their locations of theholder, said abutment forming part of a heat-reflecting screen whichsurrounds the strip-shaped heating members for the greater part andwhich touches the wall of the oven at only a few points.

6. A device as claimed in claim 1 further comprising a gas dosing systemconnected to and cooperating with said oven and said vacuum system.

7 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,645,599 Dated February 29, 1972 Inventor(s) JOHANNES MARIA VAN BRAGTIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

ON THE TITLE PAGE Insert the following where appropriate:

- Assignee: U.S. Philips Corporation, New York,

' New York Signed and sealed this 4th day of February 1975.

(SEAL) Attest:

McCOY M. mason JR. c. MARSHALL DANN Attesting Officer Comissioner ofPatents 32 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3,645,599 Dated February 29, 1972 Inventor-(s) JOHANNES MARIAVAN BRAGT It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

ON THE TITLE PAGE Insert the following where appropriate:

U.S. Philips Corporation, New York,

-- Assignee: H

New York (SEAL) Attest:

c MARSHALL DANN Comissioner of Patents McCOY M. GIBSON JR. AttestingOfficer

1. A device for uniting in a gastight manner a number of tubulararticles with sealing elements provided with electrodes at their oneends, characterized in that it comprises an oven which is adapted tocommunicate with a vacuum system and, in which at least two parallelarranged strip-shaped heating members are rigidly arranged and areconnected to a voltage source, the device furthermore comprising atleast one holder in which one end of the tubular articles which are eachprovided with a sealing member can be arranged in a row, said holderbeing arranged in the oven in such manner that each of the articles aresituated with their other end between the two strip-shaped currentconveying heating members wherein the oven comprises at least twoportions which can be separated from each other and between which asealing ring is arranged in which the heating members are secured in oneportion and the holder can be placed on or be formed by the otherportion.
 2. A device as claimed in claim 1, characterized in that thetwo heating members are manufactured from graphite.
 3. A device asclaimed in claim 2, characterized in that the two strip-shaped membersconstitute the limbs of a U-shaped heating member, which limbs arecoupled at their free ends directly to a voltage source.
 4. A device asclaimed in claim 1, characterized in that one portion is stationary andthe other portion is vertically movable.
 5. A device as claimed in claim1, characterized in that the oven comprises an internal abutment for theends of the articles to be heated which are arranged so as to beresilient in their locations of the holder, said abutment forming partof a heat-reflecting screen which surrounds the strip-shaped heatingmembers for the greater part and which touches the wall of the oven atonly a few points.
 6. A device as claimed in claim 1 further comprisinga gas dosing system connected to and cooperating with said oven and saidvacuum system.